When thawing frozen breastmilk:
Use the oldest milk first, unless recently expressed milk is advised.
Thaw breastmilk by putting the collection container in the refrigerator for several hours or overnight.
To thaw more quickly or to heat refrigerated milk, hold the container of milk under warm running water. Or place it in a cup, pot, bowl, or basin of warm water. Don't thaw milk in very hot water or in the microwave. This decreases some of the healthy properties of the milk. It can also create hot spots that may burn your child's mouth.
It's normal for your milk to separate during storage. You will see a layer of cream (fat) that has risen to the top. To mix the cream with the rest of the milk, gently swirl the bottle. Don't vigorously shake.
Tips for using thawed breastmilk include:
Milk thawed in the refrigerator must be used within 24 hours.
Milk thawed to room temperature or warmer should ideally be used in 1 to 2 hours.
If your baby didn't finish the bottle, the leftover breastmilk can still be used within 2 hours after the baby is done feeding. After 2 hours, leftover breastmilk should be discarded.
Don't refreeze milk once it has been thawed.